Chert is a fine-grained, sedimentary silica rock that typically forms nodules or layers within limestone. It is known for its conchoidal fracture and was historically prized by early humans for fashioning into sharp-edged tools and arrowheads.

Hardness

6.5-7

Mohs

Luster

Waxy

Streak

White

Transparency

Translucent

mineralcommon

Chert

Also: Flint

Hardness: 6.5-7
Luster: Waxy
Streak: White
Transparency: Translucent

Is this chert?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch chert with a known reference. Chert sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Chert leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Chert typically shows a waxy luster.
4
Match the color range
Compare against the expected color range: white, gray, brown, black, red.
5
Look at form & habit
Crystal system: trigonal. Typical habit: massive.

Often confused with

Chert vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Luster reads waxy on Chert and vitreous on Quartz.

Compare →

Often found alongside chert

Minerals reported to co-occur with chert. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: SiO₂
Mohs hardness: 6.5-7
Density: 2.6-2.65 g/cm³
Colors: White Gray Brown Black Red
Streak: White
Luster: Waxy
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Massive
Cleavage: None
Rarity: Common
Uses: Lapidary, Historical Tool Making, Decorative
Host rock: Sedimentary
Typical price: $1-20 per specimen

Where rockhounds find chert

95 mapped spots

Classic worldwide localities

United Kingdom
France
USA
Denmark
Poland

U.S. states with chert

Each link opens a state-specific list of mapped rockhounding spots that produce chert.

Field-hunting tip

Look in sedimentary country — that is the host setting where chert typically forms. If you start seeing quartz, calcite, dolomite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Florida, New Mexico, Missouri — start trip planning there.

Browse 95 U.S. spots for chert →

Common questions

How do you identify chert?+

Mohs hardness is 6.5-7. It typically shows a waxy luster. The streak is white. Common colors include white, gray, brown, black.

Where is chert found?+

Notable localities include United Kingdom; France; USA; Denmark; Poland.

Can I find chert in the United States?+

RockHoundR maps 95 chert rockhounding spots across 12 U.S. states — the top states are Florida, New Mexico, Missouri.

How much is chert worth?+

Typical asking prices fall in the range of $1-20 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like chert?+

Chert is most often confused with Chalcedony, Jasper, Quartz. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with chert?+

Chert commonly co-occurs with Quartz, Calcite, Dolomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does chert form in?+

Chert typically forms in sedimentary. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chert used for?+

Chert is used in lapidary, historical tool making, decorative.

Find chert on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.